1. Field of the Invention
The invention relates to a storage apparatus on which flash memories are mounted as storage media, particularly, relates to a storage apparatus which improves availability.
2. Description of the Related Art
In related art, mounting of hard disk drives (hereinafter, HDDs) was the mainstream as storage media for a storage apparatus such as a disk array. In recent years, the bit cost of a flash memory which is a non-volatile semiconductor memory is reducing, and applications of which are expanded from a memory card to a solid-state drive (SSD) having the same I/F as the HDD. The flash memory is excellent in power consumption at the time of idling, random-access performance, and vibration resistance as compared with the HDD. Therefore, it is expected in the future that the flash memory will be applied as a storage medium in a performance-oriented storage apparatus or a power saving-oriented storage apparatus.
Though the flash memory has the above characteristics, there are constraints in use such that there is a limit in the number of times of erasing a block as a unit of a storage area. Accordingly, as related art concerning a storage apparatus using a flash memory as a storage medium, for example, there is one in which the number of times of erasing blocks is equalized over plural flash memories (for example, JP-A-2007-265265 (Patent Document 1)).
In a system on which flash memories are mounted, plural flash memories are usually operated in parallel in order to improve performance. Therefore, the more the number of flash memories operated in parallel becomes, the more the power consumption increases. Accordingly, there is a technique in which the number of flash memories operated in parallel is selected (for example, JP-A-2007-193810 (Patent Document 2)).    [Patent Document 1] JP-A-2007-265265    [Patent Document 2] JP-A-2007-193810